The present invention relates to a process for preparing 3-dimethylaminopropylamine (DMAPA). The present invention further relates to mixtures of DMAPN and 2-(dimethylaminomethyl)-glutaronitrile (DGN) having a low DGN content.
3-Dimethylaminopropylamine (DMAPA, N,N-dimethyl-1,3-diaminopropane) is an important intermediate for industrial production of, for example, liquid soaps. DMAPA also serves as starting material for the preparation of coagulants and should itself have anticorrosive properties.
DMAPA is generally prepared by means of a two-stage process.
In the first stage, acrylonitrile (ACN) is usually reacted with dimethylamine (DMA), generally forming 3-dimethylaminopropionitrile (DMAPN).
DMAPN is then generally reduced to DMAPA in a further stage.
According to WO 2007/128803, it is advantageous to use an integrated production process or an integrated apparatus for preparing DMAPA. Here, the product stream initially obtained, which comprises DMAPN, is used directly or after purification for conversion into DMAPA in a further step. According to the teaching of WO 2007/128803, the quality of the DMAPN product stream from the first reaction (DMA and ACN) is of critical importance for the reduction reaction of DMAPN to DMAPA, in particular in respect of the consumption of the catalyst used in the reduction.
WO 2007/128803 therefore teaches a process for preparing DMAPN by continuous reaction of DMA with ACN, with firstly DMA and subsequently ACN being introduced continuously and the reaction of the reaction stream occurring in a first reaction region and at least partly in a second reaction region.
The DMAPN obtained in this way is then, generally without further work-up, reduced directly by means of hydrogen to DMAPA in a further reaction region.
According to the disclosure, the operating life of the hydrogenation catalyst in the hydrogenation of DMAPN can be increased when a DMAPN prepared according to the teaching of WO 2007/128803 in two separate reaction spaces is used in the hydrogenation of DMAPN.